(19)
(11) EP 1 484 604 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
22.12.2004 Bulletin 2004/52

(43) Date of publication A2:
08.12.2004 Bulletin 2004/50

(21) Application number: 04020249.1

(22) Date of filing: 20.04.1995
(51) International Patent Classification (IPC)7: G01N 27/407, G01N 27/419
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 21.04.1994 JP 8306994
31.01.1995 JP 1459895
08.03.1995 JP 4855195

(62) Application number of the earlier application in accordance with Art. 76 EPC:
00102029.6 / 1001262
95302646.5 / 0678740

(71) Applicant: NGK INSULATORS, LTD.
Nagoya-City, Aichi Prefecture 467-8530 (JP)

(72) Inventors:
  • Kato, Nobuhide, Intellectual Property Dept.
    Nagoya City Aichi-ken, 467-8530 (JP)
  • Nakagaki, Kunihiko, Intellectual Property Dept.
    Nagoya City Aichi-ken, 467-8530 (JP)

(74) Representative: Paget, Hugh Charles Edward et al
Mewburn Ellis LLP York House 23 Kingsway
London WC2B 6HP
London WC2B 6HP (GB)

   


(54) Method of measuring NOx concentration in a gas


(57) A method of measuring the concentration of NOx in a measurement gas, which method includes the steps of: introducing the measurement gas containing the NOx component, from an external measurement-gas space into a first internal space (6), under a first diffusion resistance; controlling the amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere having a predetermined oxygen partial pressure introducing the atmosphere from the first internal space into a second internal space (8), under a second diffusion resistance; and measuring the concentration of the NOx component present in the atmosphere in the second internal space by reducing or decomposing NOx in the gas in said second internal space so as to derive oxygen from NOx and measuring the oxygen; wherein said NOx in the second internal space consists essentially of NO, and wherein the NOx concentration is obtained based on an equation containing the pumping current due to pumping out oxygen in the second internal space.






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